In article ,
Trevor Wilson wrote:
**As I understand it (please note, I am not speaking from any real
authority here) no injector is perfect. Some are clogged a little. Some
are clogged a lot. Some are not clogged at all. Pumps are subject to
wear.

Yehbut EFI systems are closed loop and if the injectors are slightly out
of spec, the ECU will compensate. If they're wildly out an inaccurate OBC
will be the least of your worries...

As a consequence, the BEST way to measure actual fuel
consumption, is to measure the amount of fuel used, rather than
inferring how much fuel SHOULD be going into the cylinders.

That assumes you can make the perfect flow meter which will maintain its
performance.

Having said all that: My present car probably uses pulse measurement
techniques and the computer appears to be respectably accurate (though
I've never actually checked it).

I have to log all fuel bought for tax purposes so I can do a pretty
accurate check of the overall MPG - and when I have, the OBC has been as
near as dammit spot on.

--
*Being healthy is merely the slowest possible rate at which one can die.

Dave Plowman London SW
To e-mail, change noise into sound.